Mark Twain, for the record, doesn't have anything directly to do with "Mud." He didn't write it, he isn't the subject of it, and his name is never even spoken in it. His ghost, however, hovers conspicuously around the edges of writer-director Jeff Nichols' romantic slice of modern-day Americana.

Here, after all, is a riverbound adventure about two young boys who take it upon themselves to provide shelter and friendship for an adult fugitive. Their names aren't Tom and Huck, their newfound friend isn't a runaway slave named Jim, and they don't live near the end of the 19th century -- but those are all just details.

Instead, we get the soft-hearted Ellis and his parentless buddy Neckbone, proud and happy river rats who speak in cornbread drawls and who live with dirt under the nails and thorns studding the cuffs of their jeans. Mischievous but loveable, they are as close an approximation of Tom and Huck as one is likely to find in modern storytelling.

They are also charming, their story compelling, and they help make Nichols' film -- an affectionate coming-of-age tale that explores ideas of Southern manhood -- both entertaining and endearing. After bowing at Cannes last year and making its U.S. debut in January at Sundance, "Mud" opens today in New Orleans. It arrives as the first great film of 2013.

Much of the credit is due to Matthew McConaughey, who -- in only the latest in a string of wonderfully offbeat roles -- plays the grime-encrusted fugitive after whom the film is named. It certainly is the flashiest role in the movie, and McConaughey seizes it with a performance that very well could see him get the award-season recognition that largely escaped him for his deserving but largely overlooked performances last year in "Magic Mike" and the New Orleans-shot "Killer Joe."

It's that much more remarkable, then, that McConaughey's 16-year-old co-star, Tye Sheridan ("Tree of Life") -- whose eyes suggest a quiet intelligence and soulful mind -- not only holds his own as the houseboat-dwelling Ellis, but who becomes the embraceable, believable beating heart of this story.

But then, Sheridan and McConaughey -- as well as teenage co-star Jacob Lofland, who is owed a tip of the cap as Ellis' slightly dangerous but endlessly entertaining sidekick, Neckbone -- in turn owe Nichols, who wrote three wonderful characters for his stars to inhabit.

And even though his "Mud" is the sort of film that ambles easily along rather than speeding apace, it does so purposefully. His film clocks in at nearly two and a half hours, but never does one get the feeling that Nichols has anything but the firmest of grips on the rudder of this particular tale.

Set in the world of Piggly-Wigglys and pickup trucks without tailgates and people named Mae Pearl, the story centers on Ellis and Neckbone, two Southern everyboys who are utterly fascinated by things such as snakes and breasts and the sight of a 27-foot boat stranded by flood waters in the top of a tree. It's a rumor of the latter -- said to be located somewhere on a remote island in the Mississippi River near their homes -- that sets Nichols' film in motion, and sets Ellis and Neckbone on a hunt to claim it as their own.

They find the boat, too -- but much to their dismay, someone has found it before them. That would be McConaughey's Mud, and he is one of those great, gray-shaded characters that Hollywood so often shies from. He is a charmer, but there are hints of a feral danger about him -- the way he struts shirtless on the riverbank, the way he talks, the way he eyes up these two kids who have invaded his hideout. Once he warms up, he's got lots to say -- but even then, one gets the impression that you should only believe every other word. You probably shouldn't turn your back on him, either.

Mud also is in trouble -- "just a bad piece of business," he explains, shaking his head. Eventually, we learn that bad piece of business involved a beautiful woman and a necessary fight to protect her honor. Most critically, it also ended up involving a body. And so now, he needs the boys' help.

He needs them to bring him food, to bring him information, to bring him supplies for his planned getaway -- and to keep their mouths shut about it all. If they can do that, then he'll give them the boat when he doesn't need it anymore.

Honestly, though, he doesn't even need to make that promise. Because even though Ellis is a rough-and-tumble kid who is quick with his fists, he also is a closet romantic. He's been snakebit by a broken heart himself, and once he hears that Mud is motivated by true love, he's all in.

Watching "Mud" unfold, one suspects that the Arkansas-reared Nichols remembers exactly what it was like to be a boy of the Southern wilds. What's more, he seems to remember with aching clarity that moment -- accompanied by a whirl of anger, frustration and confusion -- in which boyish naivete is dashed against the river rocks by cold, harsh reality.

But "Mud" isn't as cynical as that makes it sound. Several layers of conflict bob and weave their way throughout Nichols' film, but its center is the struggle playing out in Ellis' head and in his heart. As it all flows easily but determinedly toward its conclusion, the noble Ellis must decide whether to submit and become hardened and cynical -- like every other man in his life -- or to protect that shrinking but comforting sense of hope, tattered though it may be, within him.

That's sweet and thoughtful stuff. It also is a refreshing change of pace for a Southern-set film, others of which so often tend to rely on caricature and condescension to besmirch America's drawlers.

Somewhere, one suspects, a certain old gent with a white suit and a rapier wit is nodding his cottony head in approval.

________

MUD5 stars, out of 5

Snapshot: A Mark
Twain-inspired drama about two rural boys who befriend a fugitive they
encounter on a remote island in the Mississippi River.

What works: The characters are as wonderfully drawn as they are acted, making it easy to invest emotionally in their shared story.